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Bur Oak
| colour = lightgreen | status = LR/lc | status_system = IUCN2.3 | image = Quercus macrocarpa USDA.jpg | image_width = 240px | image_caption = Bur Oak leaves and acorn / 大果櫟的葉和橡子 | regnum = Plānt | divisio = 被子植物門 / Magnoliophyta | classis = 双子叶植物纲 / Magnoliopsida | ordo = 殼斗目 / Fagales | familia = 殼斗科 / Fagaceae | genus = 栎属 / Quercus | sectio = 栎属植物列表 / Quercus | species = Q. macrocarpa | binomial = Quercus macrocarpa | binomial_authority = Michx. | range_map = Quercus marcocarpa map.png }} The leaves are 7–15 cm (3–6 in) long and 5–13 cm (2–5 in) broad, variable in shape, with a lobed margin. Most often, the basal 60% is narrower and deeply lobed, while the apical 40% is wider and has shallow lobes or large teeth. The flowers are greenish-yellow catkins, produced in the spring. The acorns are very large, 2–5 cm (0.8–2 in) long and 2–4 cm (0.8-1.5 in) broad, with a large cup that wraps much of the way around the nut, with large overlapping scales and often a fringe at the edge of the cup. Bur Oak is sometimes confused with Overcup oak and White oak, both of which it occasionally hybridizes with. Ecology Bur Oak typically grows in the open, away from forest canopy. For this reason, it is an important tree on the eastern prairies, where it is often found near waterways in more forested areas, where there is a break in the canopy. It is also a fire-resistant tree, and possesses significant drought resistance by virtue of a long taproot. New trees may, after two to three years of growth, possess a 1–2 m deep taproot. The West Virginia state champion Bur Oak has a trunk diameter of almost 3 m (9 feet). The acorns are the largest of any North American oak (thus the Latin species name macrocarpa--large fruit), and are an important wildlife food; American Black Bears sometimes tear off branches to get them. However, heavy nut crops are borne only every few years. In this strategy, known as masting, the large seed crop every few years overwhelms the ability of seed predators to eat the acorns, thus ensuring the survival of some seeds. Other wildlife, such as deer and porcupine, eat the leaves, twigs and bark. Cattle are heavy browsers in some areas. The bur oak is the only known foodplant of Bucculatrix recognita caterpillars. Cultivation and uses Bur oak makes an outstanding ornamental tree. It is one of the most tolerant of urban conditions of the white oaks, and is one of the fastest-growing of the group. It has been planted in many places north to Anchorage, Alaska and as far south as Edinburg, Texas. It withstands chinook conditions at Calgary, Alberta. The wood is high quality, and is almost always marketed as "white oak". The name sometimes is spelled "burr oak", as for example in Burr Oak State Park in Ohio, the city of Burr Oak, Kansas, the village of Burr Oak, Michigan, and in the title Burr Oaks by poet Richard Eberhart. It is also less commonly called "burl oak", as in the Burl Oaks Country Club in Mound, Minnesota. References / Riförènses / 參考資料 * *[http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233501058 Flora of North America: Quercus macrocarpa] *[http://plants.usda.gov/java/profile?symbol=QUMA2 USDA Plants Profile: Quercus macrocarpa] *[http://www.cas.vanderbilt.edu/bioimages/species/frame/quma2.htm Quercus macrocarpa images at bioimages.vanderbilt.edu] External link / Ikstörnol liŋk / 外部連結 * [http://www.portraitoftheearth.com/trees/buroak.html Quercus macrocarpa Winter ID pictures] macrocarpa Category:Trees of humid continental climate Category:Trees of Canada Category:Trees of Southeastern Canada Category:Trees of Ontario Category:Trees of Manitoba Category:Trees of Saskatchewan Category:Trees of the United States Category:Trees of the Plains-Midwest (United States) Category:Trees of the Northeastern United States Category:Flora of Massachusetts Category:Trees of Michigan Category:Trees of Alabama Category:Trees of North Carolina Category:Least concern plants Category:Trees of Kentucky Category:Trees of Ohio